Its easiest to work out how much per hour you would like to earn – keep a record of the time spent including any shopping baking time and clearing the kitchen time and work out now many hours you have spent. By adding on the ingredients and any profit you wish to make – this method means that you are rewarded properly for your time. Over time a pattern emerges as to the ‘normal’ price for a cake. In UK we do not tend to charge per slice – but normally a wedding cake would be way more than a party cake – mainly because of the fruit and marzipan involved (or the stress levels involved in a three tier fresh cake to be made only 2 days before the wedding!)